The U.S. Pat. No. 4,615,641 is the most pertinent patent known to me at the filing of this application but it lacks the structure and mode of operation set out in my claims.
There are numerous cofferdam patent structures in the prior art for effecting vessel repairs below the water-line which does not require drydocking of the damaged vessel such as the following:
______________________________________ 4,615,641 932,719 3,638,437 538,780 3,768,265 689,979 4,292,914 1,485,501 (British) 2,360,690 921,958 (USSR) 3,857,249 4,626,128 ______________________________________
The work box of my invention has no ballast tanks as shown in U.S. Pat. No. 4,615,641 to Novay. Novay does not have a waterproof membrane with tie downs which are only released to permit the membrane to rise and effect a watertight seal between the barge and work box when the water is pumped out of the barge repair box.